Oil boom and use thereof

ABSTRACT

A boom ( 1 A) is described, especially for containing oil spills and/or other similar pollution at Sea, in rivers or on water surfaces, comprising an elongate body consisting of an element having positive buoyancy relative to the surrounding medium, so that a freeboard ( 5 ) is provided, and a hanging skirt ( 6 ), which boom ( 1 A) is of the type that is usually towed behind towing vessels or is moored ( 2 ) so that the boom ( 1 A) basically forms a U-shape having side arms ( 4 ) that define a front opening ( 10 ) between them, which arms extend from a rear area or apex ( 7 ) when the towing vessels or mooring ( 2 ) pulls at the free ends of the arms of the boom ( 1 A) in order to tow the boom ( 1 A), and wherein the skirt ( 6 ) is provided with a draught that varies from a minimum size or depth in the area of the boom apex ( 7 ) to a a maximum size or depth at the free towing ends ( 15 ) of the side arms ( 4 ) of the boom ( 1 A).

The invention relates to an oil boom comprising an elongate bodyconsisting of an element having positive buoyancy relative to asurrounding medium, for example, water or the surface of the sea, and ahanging ski of the type normally towed behind towing vessels so that theboom basically forms a U-shape when the towing vessels pull the freeends of the arms of the U and tow the boom behind them to collect oilspills and/or other undesirable pollution on the surface of the sea orwater. When the boom is used in water that moves relative to the bottom,such as rivers or ocean current and the like, the situation will be thesame, except that in this case towing vessels can be replaced by fixedmooring, e.g., to the shore or the bottom. Such booms are well known,also in combination with various devices in the form of skimmers or thelike that are used to collect and remove the oil from the boom.

Thus, the invention relates to an oil boom as disclosed in the preambleof independent patent claim 1 and a use thereof as disclosed in patentclaim 10.

The hanging part of the skirt or the so-called skirt depth of the boomsof this type is as a rule uniform or constant/unvarying along the wholeextent of the boom. This means that large parts of the arms of theU-boom are pulled or towed substantially parallel with each other sothat large parts of the boom arms do little to contribute to a largerfront opening.

This front opening is crucial for the area coverage of the boom asregards the containment area. The ratio between the length of the boomand the front opening is called the gap ratio, which is the opening ofthe boom divided by the length of the boom. The more powerful the boatsin relation to the size of the boom and the speed at which it is towed,the greater the possible gap ratio. In use, a gap ratio of 0.4 istypical, i.e., that a boom of 200 metres has a front opening of 80metres.

Of course, it is conceivable that the towing vessels might not tow in asubstantially parallel direction, but in markedly diverging directions,i.e., at an angle outwards from each other in order to increase thefront opening. However, a solution of this kind has in practice beenfound to be almost useless, in particular if the tow is to be carriedout at a reasonably acceptable speed. Even if a solution of this kind ischosen, the boom arms will still be parallel at the front, although fora shorter distance.

As additional examples of the prior art reference can be made to U.S.Pat. Nos. 3,579,994 and 3,922,862 and also to GB Patent 1 400 766.

The '994 patent teaches a barrier or blocking device for control ofsubstances in bodies of water comprising a hanging skirt havingpermanent ballast along its lower edge. A variant of the device isespecially designed for shore anchoring and the skirt portions closestto the shore areas, i.e., the anchoring ends, are stepped so that theskirt will be better adapted to the depth of the beach zone.

The '862 patent teaches a boom device designed to be towed forcontainment of contaminants. One of the features of the device is ahanging skirt having a depth that varies from a maximum at the apex ofthe boom to a minimum at the towing ends. The patent is especiallydirected towards details of the design and the varying depth asmentioned above.

The GB patent relates to a floating boom having a hanging ballastedskirt, the depth of which may be varied. The object is to make it easierto tow the boom into place as the depth is reduced during such anoperation in order to lessen the towing drag and to enhancemanoeuvrability, and subsequently to adjust the depth to the actual areaof use.

The object of the invention is in a simple and efficient manner toensure optimal area coverage for oil booms and the like, which none ofthe cited documents suggest, teach or indicate. This is achieved with aboom of the type mentioned in the introduction which is characterised bythe features disclosed in the characterising clause of independentpatent claim 1.

Advantageous embodiments of the invention are disclosed in the dependentpatent claims.

The invention will now be described with reference to the drawings,wherein;

FIG. 1 is a schematic illustration of a conventional oil boom beingtowed by two towing vessels;

FIG. 2 is a schematic illustration of a boom according to the inventionunder similar conditions as those shown in FIG. 1, compared with aconventional boom;

FIG. 3 is a schematic side view of one of the arms of the boom accordingto the invention;

FIG. 4 is a side view like that in FIG. 3, but showing both arms;

FIG. 5 is a side view like that in FIG. 4, but with a concave reductionin the depth of the skirt;

FIG. 6 is a side view like that in FIG. 5 but with a stepped variationof the depth of the skirt;

FIG. 7 is a schematic illustration of the boom according to theinvention used together with a boom apex device that straightens partsof the boom;

FIG. 8 is a schematic view of the boom according to the invention usedtogether with a skimmer or the like connected at the apex of the boom;

FIG. 9 is a schematic view of the boom according to the invention usedas an open lead boom, followed by a conventional boom;

FIG. 10 is a schematic view of the boom according to the invention usedas a lead boom with boom arms of different lengths; and

FIG. 11 is a schematic illustration of a second embodiment of the skirtof the boom according to the invention, and two side views of such aboom.

FIG. 1 shows a typical U-boom configuration. The arrow A in the figureindicates the tow direction or relative direction of travel relative tothe water when the boom is used in, e.g., rivers or other waters subjectto currents. The reference numeral 1 indicates the actual boom and thereference numeral 2 a towing vessel, or anchoring point when the boom isused in a river. The boom 1 is towed or pulled, optionally anchored,using two lines 3 fastened to the free ends 15 of the boom 1 side arms 4and to two towing vessels 2. The towing vessels 2 are at a suitabledistance from each other and move forward substantially in parallel, sothat the characteristic U-shape is produced, the boom 1 being made of aflexible material with a conventional flotation body to ensure that ithas freeboard, and a hanging skirt, which skirt extends the same depthalong the whole boom 1. The U-shaped boom 1 thus forms a front opening10 defined by the side arms 4 which come together in an apex 7, when theboom is not terminated in a rigid rear portion and/or connected directlyto a skimmer or the like. As can be seen from FIG. 1, it is only thefront opening 10 and a boom portion 12 that are oriented at 90 degreesto the tow direction, and large parts of the side arms 4 are roughlyparallel in the area B and thus do not contribute significantly to thecoverage area when containing oil spills or other undesirable pollution.

FIG. 2 is a schematic illustration of a boom 1A according to theinvention compared with a conventional boom 1, where the conventionalboom 1 is indicated in broken lines. As indicated in FIG. 2, theinvention provides an additional front opening 11.

This is because in the areas indicated by the letter C the boom islaterally displaced outwards, thus achieving something close to an“otter effect”, which per se is a familiar phenomenon for many amateurfishermen. This displacement is achieved in that the boom skirt 6 ismade having a skirt length that varies from a minimum in the area at theapex 7 to a maximum at the free ends 15 of the side or boom arms 4, ascan be seen from the schematic side view of the boom arm 4 of the boom1A in FIG. 3.

FIG. 4 is a view of the whole boom 1A according to the invention whereboth boom arms 4 are connected together at the apex 7 where the depth ofthe skirt 6 varies linearly from the apex 7 to the free ends 15 of theboom. The skirt depth can also be varied non-linearly in the form of aconcave configuration as can be seen from FIG. 5, or in steps as can beseen from FIG. 6. These exemplary embodiments of the design of the depthvariation of the skirt are not considered to be limiting for theinvention, as the depth can clearly be varied within wide limits withoutdeparting from the principle of the invention.

How much the skirt depth or draught is to vary depends on the primaryarea of use of the boom and the length or size of the boom and primarytowing speed. In practice a minimum draught in the range of 0.1 to 0.6metres and a maximum draught in the range of 0.6 to 2 metres has beenfound suitable when the oil is to be guided into a connected skimmer orthe like which continually guides the oil away from the apex. If the oilis to be held in the apex for later skimming, the minimum depth at theapex can advantageously be increased to more than the given 0.1 to 0.6metres. These examples of size are not considered to be limiting for theinvention, as they can clearly be varied within wide limits withoutdeparting from the principle of the invention.

FIG. 7 shows the boom 1A according to the invention wherein at the boomapex 7 there is mounted or attached a device 9 in the form of a localdeep skirt, deep skimmer or drag anchor or the like which producesrelatively large drag in the water relative to the shallow skirt 6 atthe boom apex 7. The part D of the boom 1A which is closest to the boomapex 7 will then extend in a more or less straight line. This allowsincreased towing speed of the boom without the loss of oil, as thegreatest loss of oil under the skirt, so-called entrainment, occurs whenthe boom is at 90 degrees to the tow direction and this angle is reducedalong the whole extent of the boom.

FIG. 8 shows a standard boom 1 and a boom 1A according to the inventionin use as lead boom in front of a device 9, the purpose of which iseither to further concentrate the oil, store the oil, separate the oil,skim the oil, pump the oil up or combinations thereof. This device 9 maybe according to known technology in the form of a vessel with a skimmerat its bow, an inline skimmer, a NOFI VEE SWEEP or the like.

FIG. 9 shows the boom 1A according to the invention which is especiallydesigned for containment at low speeds, where it is to cover arelatively large area by gathering the oil together. Advantageously, theboom can then be combined with a conventional boom such as a standardU-boom 1 that is towed behind the boom 1A which is then provided with acollecting or funnel-like opening at the apex 7 that is held joinedtogether at the bottom of the skirt by means of a chain 8 or the like.

FIG. 10 is a schematic illustration of the boom 1A used together with askimmer or the like joined or connected directly to the boom apex 7 or arear portion. The boom 1A in FIG. 10 is dimensioned and especiallydesigned for containment at high speeds, and a so-called NOFI Current orOcean Buster 14, as described in the Applicant's NO Patent ApplicationNo. 20003952, is used. In this case, the port 12 part of the boom 1A isconnected to a towing vessel 2 and the port boom 12 is shorter than thestarboard boom 11. On each side of the boom apex 7 the boom arm 4 may bevaried in length, size and degree of tapering of the skirt for certainconfigurations, e.g., for operation close to vessels where one arm 12close to the shipside is much shorter than the arm that runs out towardsthe other tow boat.

Other modes of use that are not illustrated in the figures are of coursealso possible. When the boom is used in waters subject to currents, suchas a river, where it is desirable to guide the oil in towards the riverbank, it is quite possible to do so using just one of the boom armsaccording to the invention. Since the boom according to the inventionwill give a better coverage area, it will be possible in this case tomanage with fewer booms or a boom that is shorter in length comparedwith a conventional boom.

There are a number of systems for replacing one of the two tow boatswhen the boom is used in open seas. The boat may be replaced by anoutrigger that holds the free end of the boom out, or by anotterboard-like or trawl door-like device, the purpose of which is todraw one of the boom arms away from the tow boat and thus permit towingof the boom using just one boat. Of course, the boom according to theinvention may advantageously be used in combination with these devices,as basically the boom will more easily move outwards into an optimalshape. This also applies in connection with the use of a ropes, forexample, in the form of a crow's foot, to control the position of one ormore points on the boom from one or both tow boats.

FIG. 11 is a schematic illustration of a second embodiment of the skirt6 in which a so-called integral apex is formed. In the actual apex areaor at the apex 7, the skirt 6 is made having a greater depth beforebecoming a shallower portion which in turn increases in depth towardsthe free ends 15 of the side arms 4. This type of boom 1A can at regularintervals in the skirt 6 be fastened directly to the bottom tensionmember or bottom chain 8, or in some areas it can be made with an opennet or netting 13 between the skirt 6 and a bottom chain or bottomtension member 8. The embodiment will impart a more V-shaped boom formto the lead boom 1A during towing as there is a marked tension or dragon the apex 7. At the same time, the part of the boom apex 7 with a deepskirt will to some extent move into a traditional U-boom configurationso that it locally establishes a marked apex 7 where the oil iscollected and concentrated prior to skimming, which is some cases may bedesirable, for example when used together with certain types ofskimmers, or when there is a desire for a long continuous boom which canbe coiled up on a boom reel like a standard boom.

Although this is not described in more detail, it goes without sayingthat the boom 1A may be made so that it can be sectioned. For instance,it may be expedient to split or divide the boom at the apex 7 so as toproduce two identical boom halves, each of which can function asindependent booms. It may also be possible to carry out furthersectioning so that boom lengths can almost be “tailor-made”. Thesections can in turn be produced in such manner that they can easily bejoined together. How this is to be done in practice is a part of thegeneral technical knowledge in the field.

Although the invention above is described by means of exemplaryembodiments, these embodiments must only be seen as illustrative and notlimiting for the invention as defined in the attached patent claimswhich are intended to cover all equivalents and the like.

1. A boom (1A) for containing pollution on water surfaces, comprising anelongate body with an element having positive buoyancy relative to thesurrounding water, so that a freeboard (5) is provided, and a hangingskirt (6), which boom (1A) is of the type that may be towed behindtowing vessels (2) so that the boom (1A) basically forms a U-shapehaving side arms (4) that define a front opening (10) between them,which arms extend from a rear area apex (7) when there is tension on thefree ends of the arms of the boom (1A) in order to tow the boom (1A),characterised in that the skirt (6) is provided with a draught thatvaries from a minimum size in the area at the boom apex (7) to a maximumsize at the free towing ends (15) of the side arms (4) of the boom (1A).2. A boom according to claim 1, characterised in that the boom (1A) isproduced in such manner that it can be split at the apex area (7),thereby producing two substantially identical boom halves, each of whichcan be used separately as a boom.
 3. A boom according to claim 1,characterised in that the boom arms (4) have different lengths.
 4. Aboom according to claim 1, characterised in that the boom arms (4) canbe sectioned so that units are provided which can function separately asan independent boom (1A), or and may be joined together.
 5. A boomaccording to claim 1, characterised in that the draught of the skirt (6)varies in at least one of a linear, a concave or stepped manner, or acombination of variations.
 6. A boom according to claim 1, characterisedin that only one of the arms of the boom (1A) extends out from the apex(7) when in use.
 7. A boom according to claim 1, characterised in thatthe skirt (6) is made integral with the boom apex (7), the skirt beingmade having a greater draught at the apex (7) than in the adjacentportions which are made having a minimum draught before the skirt (6)again increases in draught.
 8. A boom according to claim 1,characterised in that the skirt has a minimum draught of about 0.1metres and a maximum draught of 3 metres.
 9. A boom according to claim1, characterised in that the boom arms (4) or the whole boom (1A) withtwo boom arms (4) is moored in a current of water.
 10. The use of theboom according to claim 1, connected to at least one of an inlineskimmer, apex boom or the like at the boom apex (7) for collecting oilspills or the like.
 11. A boom according to claim 2, characterised inthat the boom arms (4) have different lengths.
 12. A boom according toclaim 2, characterised in that the boom arms (4) can be sectioned sothat units are provided which can function separately as an independentboom (1A) and be joined together.
 13. A boom according to claim 3,characterised in that the boom arms (4) can be sectioned so that unitsare provided which can function separately as an independent boom (1A)and be joined together.
 14. A boom according to claim 2, characterisedin that the draught of the skirt (6) varies in at least one of a linear,a concave or stepped manner, or as a combination of variations.
 15. Aboom according to claim 3, characterised in that the draught of theskirt (6) varies in at least one of a linear, a concave or steppedmanner, or as a combination of variations.
 16. A boom according to claim4, characterised in that the draught of the skirt (6) varies in at leastone of a linear, a concave or stepped manner, or as a combination ofvariations.
 17. A boom according to claim 3, characterised in that onlyone of the arms of the boom (1A) extends out from the apex (7) when inuse.
 18. A boom according to claim 4, characterised in that only one ofthe arms of the boom (1A) extends out from the apex (7) when in use. 19.A boom according to claim 5, characterised in that only one of the armsof the boom (1A) extends out from the apex (7) when in use.
 20. A boomaccording to claim 2, characterised in that the skirt (6) is madeintegral with the boom apex (7), the skirt being made having a greaterdraught at the apex (7) than in the adjacent portions which are madehaving a minimum draught before the skirt (6) again increases indraught.
 21. A boom according to claim 3, characterised in that theskirt (6) is made integral with the boom apex (7), the skirt being madehaving a greater draught at the apex (7) than in the adjacent portionswhich are made having a minimum draught before the skirt (6) againincreases in draught.
 22. A boom according to claim 4, characterised inthat the skirt (6) is made integral with the boom apex (7), the skirtbeing made having a greater draught at the apex (7) than in the adjacentportions which are made having a minimum draught before the skirt (6)again increases in draught.
 23. A boom according to claim 5,characterised in that the skirt (6) is made integral with the boom apex(7), the skirt being made having a greater draught at the apex (7) thanin the adjacent portions which are made having a minimum draught beforethe skirt (6) again increases in draught.
 24. A boom according to claim6, characterised in that the skirt (6) is made integral with the boomapex (7), the skirt being made having a greater draught at the apex (7)than in the adjacent portions which are made having a minimum draughtbefore the skirt (6) again increases in draught.
 25. A boom according toclaim 2, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 26. A boom according toclaim 3, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 27. A boom according toclaim 4, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 28. A boom according toclaim 5, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 29. A boom according toclaim 6, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 30. A boom according toclaim 7, characterised in that the skirt has a minimum draught of about0.1 metres and a maximum draught of 3 metres.
 31. A boom according toclaim 2, characterised in that the boom arms (4) or the whole boom (1A)with two boom arms (4) is moored in a current of water.
 32. A boomaccording to claim 3, characterised in that the boom arms (4) or thewhole boom (1A) with two boom arms (4) is moored in a current of water.33. A boom according to claim 4, characterised in that the boom arms (4)or the whole boom (1A) with two boom arms (4) is moored in a current ofwater.
 34. A boom according to claim 5, characterised in that the boomarms (4) or the whole boom (1A) with two boom arms (4) is moored in acurrent of water.
 35. A boom according to claim 6, characterised in thatthe boom arms (4) or the whole boom (1A) with two boom arms (4) ismoored in a current of water.
 36. A boom according to claim 7,characterised in that the boom arms (4) or the whole boom (1A) with twoboom arms (4) is moored in a current of water.
 37. A boom according toclaim 8, characterised in that the boom arms (4) or the whole boom (1A)with two boom arms (4) is moored in a current of water.
 38. The use ofthe boom according to claim 2, connected to an inline skimmer, apex boomor the like at the boom apex (7) for collecting oil spills or the like.39. The use of the boom according to claim 3, connected to at least oneof an inline skimmer, apex boom or the like at the boom apex (7) forcollecting oil spills or the like.
 40. The use of the boom according toclaim 4, connected to at least one of an inline skimmer, apex boom orthe like at the boom apex (7) for collecting oil spills or the like. 41.The use of the boom according to claim 5, connected to at least one ofan inline skimmer, apex boom or the like at the boom apex (7) forcollecting oil spills or the like.
 42. The use of the boom according toclaim 6, connected to at least one of an inline skimmer, apex boom orthe like at the boom apex (7) for collecting oil spills or the like. 43.The use of the boom according to claim 7, connected to at least one ofan inline skimmer, apex boom or the like at the boom apex (7) forcollecting oil spills or the like.
 44. The use of the boom according toclaim 8, connected to at least one of an inline skimmer, apex boom orthe like at the boom apex (7) for collecting oil spills or the like. 45.The use of the boom according to claim 9, connected to at least one ofan inline skimmer, apex boom or the like at the boom apex (7) forcollecting oil spills or the like.